Conventionally, thin-film deposition in semiconductors, electronic components, and solar cells and the like uses a vacuum processing apparatus that carries out processing on a substrate by using a plasma.
Examples of such vacuum processing apparatuses include film depositing apparatuses, plasma CVD (Chemical Vapor Deposition) apparatuses, dry etching apparatuses, and sputtering apparatuses.
For example, in the case in which film deposition of an amorphous silicon or a microcrystalline silicon or the like is carried out on a substrate in a plasma CVD apparatus, a film deposited and is deposited on portions other than the substrate (for example, the discharge electrode, the counter electrode, substrate holding fixture, electrode cover and the like, which are referred to hereinbelow as the “film deposition unit members”) that face toward the plasma generated inside a film deposition chamber.
When their film becomes thick, there is a concern that, for example, the film will separate due to thermal expansion differences caused by temperature changes inside the film deposition chamber during the film deposition process for each substrate, and that this film will be mixed into the film that is being formed on the substrate causing a deterioration of the film deposition quality, or a concern that particles that hinder film deposition will be produced. When this type of situation occurs, defective products increase, and thus, the processing capacity of the film deposition apparatus decreases.
Because of this, the film deposition operation is suspended, and a cleaning that removes the film that has formed inside the film deposition chamber is performed.
During this cleaning, normally the film deposition apparatus is left open in the atmosphere and the film deposition unit members inside the film deposition chamber, on which a film has deposited, are manually replaced with replacement components that have had the film removed by washing at a separate location. However, besides the replacement operation for necessary components, in order to open the apparatus to the air, there is a problem in that time and labor are consumed in order to lower the temperate of the substrate heater, to break the vacuum, to raise the temperature again, and to draw a vacuum again.
As a method for eliminating this problem, for example, a self-cleaning procedure has been proposed in which a cleaning gas that includes fluorine is introduced into the film deposition chamber, a fluorine radical (F) is produced by a plasma, and this fluorine radical (F) removes the film by etching (refer to patent document 1 and patent document 2).
In this case as well, reducing the self-cleaning procedure time is necessary in order to improve the processing capacity of the film deposition processing apparatus, and thus, measures to improve the cleaning speed at which film is removed by etching is treated as a key problem. In addition, with respect to the self-cleaning procedure operation, performing the self-cleaning procedure after a plurality of film deposition operations has been proposed.
The invention disclosed in patent document 1 performs self-cleaning procedure at various film thicknesses, finds continuously processable integrated film thicknesses in a range in which the temperature of the discharge electrode (which is also serves as a supply means for the film-depositing gas) opposed to the substrate is between 200° C. and 400° C., and determines the self-cleaning procedure cycle by dividing this integrated film thickness by an upper limiting value of the substrate film deposition thickness. Specifically, the self-cleaning procedure is performed every eleven sheets (an integrated film thickness of 11 μm) so that contamination by impurities does not occur.
In addition, the invention disclosed in patent document 2 discloses carrying out cleaning after CVD procedure has been performed “n” times, where “n” indicates a state lower than than a predetermined total particle threshold limit, a state higher than a predetermined uniformity limit, or an upper limit to the number of processes that a CVD apparatus can have in operation within a predetermined deposition rate.
In a specific example of cleaning residual material from a CVD apparatus, “n” is in a range of about 1 to 50, preferably 2 or greater, and more preferably 10 or greater.
A substrate is conveyed into a film deposition chamber that is provided with a particle counter before the film deposition operation, and after preparatory operation is performed, the number of particles on the substrate is measured. As a result of the measurement, this “n” is set in a range in which the particles remain within a predetermined number of particles.
Alternatively, “n” is set in a range in which the fluctuation in the film deposition thickness remains within a predetermined range (a predetermined uniformity).
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2003-163208
[Patent Document 2]
Japanese Unexamined Patent Application, First Publication No. H9-232299
However, the inventions disclosed in patent document 1 and patent document 2 lack general applicability in that, for example, both set the time interval between the self-cleaning procedures after performing preparatory operations, and thus, this setting consumes time, and in addition, the setting must be calibrated again each time the film deposition conditions change.
In addition, in order to suppress explosive reactions due to a film deposition source gas coming into direct contact with the cleaning gas, the gas supply system piping lines and the exhaust piping lines must be purged and switched. Because this operation requires time, the self-cleaning procedure operating time increases. Thereby, in order to appropriately adjust the cleanliness inside the film deposition chamber and the self-cleaning procedure frequency, a judgment is necessary based on the operation conditions experimentally obtained by repeatedly implementing the self-cleaning procedure trials.
In addition, although improvements in the self-cleaning procedure methods can be seen that are due, for example, to adjusting the location for feeding the cleaning gas in order to increase the time interval between the self-cleaning procedures, these cannot be said to be sufficient, and further improvement is required.
In particular, for example, in an apparatus such as a thin-film solar cell, in which the films that are formed are thick in comparison to the films that are formed during the manufacture of a TFT for a liquid crystal display, the self-cleaning procedure must be performed on a thick film that is deposited inside a film deposition chamber after performing film deposition processing a plurality of times, and thus, in order to increase the operating time of the vacuum processing apparatus, the self-cleaning procedure time must be reduced. Thus, because the amount of cleaning gas and amount of the etching reaction applied to the deposited film per unit of time become large, the amount of heat energy that is generated during the self-cleaning procedure becomes large, and the temperature of the film deposition unit members inside the film deposition chamber rises rapidly. In particular, in the case in which the self-cleaning procedure is performed at an etching rate of several nm/s or greater, the amount of heat energy that is generated cannot be decreased, and generally during the manufacturing of a thin film solar cell, the self-cleaning procedure operation is a difficult problem, and the timing for suitable self-cleaning procedure becomes extremely important.
In consideration of the problems described above, it is an object of the present invention to provide a vacuum processing apparatus that can set a time interval for performing self-cleaning procedure simply and so as to have general-use applicability, and furthermore, can further increase the time interval between self-cleaning procedures and can improve production efficiency, and an operating method therefore.